Synthetic detergents typically consist of a dispersant, a builder, and other miscellaneous ingredients such as brighteners, perfumes, anti-redepositon agents and enzymes. The dispersant typically comprises a surfactant and functions to separate dirt, soil and stains from fabric and other substrates. Polyacrylates are well known and commonly used dispersant compounds. The builder binds with and forms a complex with metal cations, such as calcium and magnesium ions found in “hard water,” which otherwise interfere with the dispersant activity. Such binding and complex formation is also commonly referred to as “chelating” and compounds capable of such interaction with metal ions are known as “chelating agents.”
Phosphates are excellent chelating agents, which is why they were historically used as builders for detergents. However, large amounts of phosphorus were released to streams, rivers, lakes and estuaries, even after wastewater treatment. In natural water bodies, phosphorous acts as a fertilizer, increasing growth of algae and aquatic weeds, which depletes oxygen available for healthy fish and aquatic life, whose numbers then decrease. Consequently, most jurisdictions have limited or banned the use of phosphates in detergents.
In the search for phosphate substitutes, amino carboxylate compounds have been found to be effective chelating agents and, therefore, useful as builders for laundry and automatic dishwashing detergents. For example, U.S. Pat. No. 3,331,773, teaches preparation of water soluble polymers having chelating functionality by grafting water soluble chelating monomers onto water soluble polymers. Diethylenetriamine, ethylenediamine tetraacetic acid, and other polyalkylene polyamine polyacetic acids are identified as examples of chelating monomers suitable for grafting onto water soluble polymers.
U.S. Pat. No. 5,514,732 also describes contact lenses made from water insoluble polymers having chelating functionality. The polymers are made from aminopolycarboxylic acids with a polymerizable olefinic group, as well as a hydrophilic monomer and one or more crosslinking monomer.
U.S. Patent Application No. 2008/00262192 describes an water-soluble polymer having a high chelating performance and clay dispersancy which is made by polymerizing an amino group-containing allyl monomer derived from adding an amine compound, such as iminodiacetic acid (IDA), to an allyl monomer, such as allyl glycidal ether (AGE). Also according to U.S. Patent Application No. 2008/00262192, the amino group-containing allyl monomer may be polymerized with other polymerizable monomers including, without limitation, unsaturated monocarboxylic acid monomers.
U.S. Patent Application No. 2009/0082242 discloses a phosphate free dish washing liquor comprising exfoliated nanoclay, a clay-dispersing polymer, as well as other components including known chelating agents such as nitrilotriacetates (NTA), ethylene diamine tetra acetate (EDTA), propylene diamine tetraacetic acid, (PDTA), ethylene diamine N,N′-disuccinic acid (EDDS) and methyl glycine diacetic acid (MGDA), or their salts.
The present invention provides novel polymerizable monomer compounds which are water soluble and have chelating functionality, as well as polymers made therefrom which shall be useful in aqueous systems for scale inhibition, soil removal, tea destaining, particulate dispersion and metal ion binding.